with the shallow DOF and free of distortion with a lens in the 20-28mm range unless I back up and go longer lens? This would not be the same look, and at times may be impossible due to space restrictions.
With a lens "in the 20-28mm range" -- you'll be fine with faces as long as your goal is NOT to be flattering to your subject.
The 2x crop factor isn't converting your 25mm to a 50mm -- rather -- you're just zooming in on your 25mm. Furthermore, just backing up changes the focus equation -- so you're not getting the same image out of your 50mm as before by backing up twice the original distance.


